1. Field of the Invention
The present invention relates to a node apparatus, a node quantity adjustment method, and tangible machine-readable medium thereof for a sensor network. More specifically, the present invention relates to a node apparatus, a node quantity adjustment method, and tangible machine-readable medium thereof for reducing the data transmission loading in a sensor network.
2. Descriptions of the Related Art
Due to the fast development of wireless communication technology and the needs of environment monitoring, such as monitoring the consistency of carbon dioxide or water levels in tunnels, wireless sensor networks have been widely used to detect various changes in the environments over recent years.
In particular, sensors of the wireless sensor network can be deployed at different locations in a geographic environment, and these sensors are called nodes. Since the nodes communicate and transmit data with each other wirelessly, the wireless sensor network is flexible and does not need an extra charge for deployment. These nodes are configured to retrieve the surrounding environment information, such as temperature, humidity, consistency of gas, or movement of an object. The nodes then transmit the environmental information to a data sink (one of the nodes) to decipher changes in the geographic environment.
According to the property of the geographic environment, the topologies of wireless sensor networks can be divided into two types: a tree type or a link type. In the tree type wireless sensor network, the deployment of nodes has a higher density. Each node in the tree type wireless sensor network has several neighbor nodes. On the contrary, the nodes are deployed in line in the link type wireless sensor network. Usually, there are only two neighbor nodes.
However, the distance between the terminal nodes and data sink will be increased when the quantity of nodes in the wireless sensor network increases. To ensure that the data sink can receive data from the terminal nodes effectively, it consequently costs more resources (e.g. power) for the wireless sensor network to transmit data from the terminal nodes. Moreover, when the quantity of nodes increases, the data transmission that is loading in the wireless sensor network also increases at the same time to cause a higher packet missing rate. Based on the deployment property of the nodes, the problems described above will be more obvious in the link type wireless sensor network.
In view of this, it is important to improve the efficiency of data transmission and to reduce data loading in the wireless sensor networks.